1. Field of the Invention
The present invention relates generally to semiconductor devices, and more specifically to semiconductor devices containing both a power transistor and integrated control circuitry.
2. Description of the Prior Art
An object of the present invention is to provide a monolithic semiconductor device containing an integrated control circuit and at least one power transistor integrated into the same chip. Another object is to provide a process for manufacturing such a device.
In known monolithic devices of the above-mentioned type, the control circuit usually comprises several low voltage transistors. A P-type diffused horizontal isolation (DHI) region is obtained by selective dopant implantation and subsequent diffusion. The DHI region gives rise, together with the collector regions of the power transistor and an N-type buried layer (BL FIG. 1), to a parasitic NPN transistor whose firing should be avoided. This involves the formation of a very deep junction and very critical dopant profile design.
These design constraints reflect adversely on device performance, cost, and production yields.
A monolithic semiconductor device fabricated in accordance with the present invention overcomes these drawbacks and provides additional advantages.